1. Field of the Invention
Methods consistent with the present invention relate to manufacturing a ferroelectric thin film for data storage, and more particularly, to a method of manufacturing a ferroelectric thin film with good crystallinity and improved surface roughness.
2. Description of the Related Art
With the recent advances of data storage technology, the recording density of data storage devices, such as hard disks or optical disks, has increased to 1 Gbit/inch2 or more. The rapid development of digital technology is requiring even higher capacity data storage devices. However, as for the conventional data storage devices, the maximum recording density is limited due to superparamagnetic limits or laser diffraction limits. Research has recently been carried out into the development of data storage devices with a density over 100 Gbit/inch2 which overcome the diffraction limit using near-field optics.
On the other hand, research has been carried out into the development of high capacity data storage devices using tip-shaped probes as can be found in atomic force microscopy (AFM). Since tip-shaped probes can be downsized to several nanometers, atomic level surface microstructure can be observed using such tips. Theoretically, terabit data storage devices can be made using tip-shaped probe recording. Recording media and recording methods are important factors determining the performance of tip-shaped probe based data storage devices. Among the media, a ferroelectric recording medium stands out and thus has been subject to study.
FIG. 1 is a cross-sectional view of a conventional ferroelectric recording medium.
Referring to FIG. 1, a bottom electrode 4 and a recording medium layer 8 are sequentially stacked on a substrate 2. The recording medium layer 8 is made of a ferroelectric thin film such as a PbTiO3 thin film, a PbZrxTi(1-x)O3 (PZT) thin film, or a SrBi2Ta2O9 (SBT) thin film. When a voltage pulse is applied between the bottom electrode 4 and an AFM tip 9, the polarization of the ferroelectric media can be locally changed. Depending on the sign of the voltage, up or down polarization can be written. The read-out of the polarization state can for example be detected using a resistive probe. For more information on the structure and operation of the ferroelectric recording medium, refer to Korean Patent Registration No. 0379415.
The recording medium, using the ferroelectric thin film has advantages of high data writing speed, low power consumption, and data rewriting. However, the recording medium using the ferroelectric thin film has a disadvantage of short data retention time. Also, since the ferroelectric thin film is polycrystalline, it has poor surface roughness due to grain boundaries. Due to the poor surface roughness, it takes a long time to adjust a distance between the AFM tip 9 and the recording medium layer 8, thereby lowering data reading and writing speeds and wearing out the AFM tip 9.